Which of the following parental combination has produced mutant offspring?

All the sons are haemophilic and daughter are normal of a haemophilic father and normal mother. This character is

Select the incorrect statemant from the following.

Complete dominance is absent in

The sex in Drosophila melanogaster is determined by

In a gene pool, along with beneficial mutations those mutations also exists which are damaging to an individual. It has been found that these mutations are irreversible because

$I.$ they have survival value

$II.$ they are acquired

$III.$ they are recessive and carried by heterozygous individuals only

$IV.$ they show genetic drift

Choose the incorrect option for given statement